The invention relates to hydrocarbon production, and in particular, to a pressure control assembly for working pipe in a well under pressure.
Conventional petroleum extraction often leaves a significant amount of un-recovered petroleum in petroleum reservoirs. One way to increase recovery is to develop the reservoir with a very high density of producing wells. This option is, however, very expensive and often not economic. One proposal for increasing well density, however, is to drill the producing wells into the reservoir from a subterranean mine excavation located below the petroleum reservoir. Such upward extending wells are often referred to as drain holes, because fluids drain down through the well during production. The economics of drilling wells to a very dense spacing can be more favorable, because each of the producing wells drilled from such a subterranean location will typically be much shorter than wells drilled from a surface location in a conventional manner. This is because the subterranean mine excavation is located much closer to the petroleum reservoir. In addition, expensive drill mud is not needed. Since only water is used to cool the drill bit and there is no backpressure in the drill hole, natural reservoir permeability is not contaminated. Further, drains are produced by gravity, well pumps are not needed. Production through a subterranean mining excavation is potentially an option both for initial development of new reservoirs and for further development of reservoirs that have already been partially depleted by conventional production from production wells drilled from surface locations.
One complication with drilling drain holes and producing petroleum from a subterranean mine excavation located below a petroleum reservoir is that drilling and other well operations must ordinarily be conducted under pressure. Because the drain holes extend in an upward direction, there will always be a positive pressure exerted at the wellhead, which wellhead could be a drilling stack or any other wellhead configuration used for conducting other well operations. This pressure will typically equal the pressure exerted by the reservoir plus the hydrostatic head of fluid filling the drain hole. This is significantly different than conventional operations conducted from a surface location. In the conventional situation, drilling and other well operations are typically conducted without positive pressure at the wellhead, because the well is filled with a liquid that provides a hydrostatic head to counterbalance the reservoir pressure. In the conventional situation, well operations are ordinarily performed under pressure only under upset conditions, such as when there has been a sudden influx of fluid into the wellbore during drilling. As a result, conventional blowout preventers and other conventional wellhead components are typically not designed for normal continuous operation under pressure. These conventional wellhead components are, therefore, typically not well suited for performing drilling or other well operations on drain holes that extend in an upward direction from a subterranean mine excavation, and there is a significant need for improved apparatus and techniques for performing drilling and other operations in such drain holes.
The present invention addresses the need for performing normal drilling and other well operations under pressure at the wellhead through the use of a special annular sealing structure for sealing the annular space around pipe that is to be manipulated in a well to perform the operation. The sealing structure involves maintenance of a seal between an annular sealing wall and the outside of the pipe in a way that accommodates movement of the pipe under pressure during well operations. In particular, the sealing structure involves a sealing wall with at least one fluid port extending through the sealing wall so that a hydrodynamic bearing fluid is injectable into the annular space between the sealing wall and the outside surface of the pipe. The hydrodynamic bearing fluid helps to maintain a good annular pressure seal while at the same time providing significant lubrication between the sealing wall and the pipe, significantly reducing wear to the sealing wall from manipulation of the pipe during operations performed under pressure.
One aspect of the invention involves a well pressure control assembly. In one embodiment, the well pressure control assembly is operably connectable to a well, typically through a flange connection to well casing, and includes an annular pressure containment structure including the noted sealing structure. The annular pressure containment structure has a passage through which pipe is moved into and out of the well and in which the pipe can be rotated, such as during drilling operations. The annular pressure containment structure includes a sealing wall that defines at least a portion of the passage and includes at least one fluid port extending through the sealing wall adjacent to the passage. When a pipe is received in the passage, hydrodynamic bearing fluid is injectable though the fluid port into the passage adjacent the pipe. In a preferred embodiment, hydrodynamic bearing fluid distributes evenly circumferentially around the pipe so that a liquid film develops between the sealing wall and the pipe, resulting in the development of a hydrodynamic bearing that maintains a standoff between the sealing wall and the pipe.
One alternative for enhancing performance of the annular pressure containment structure is to provide the sealing wall as a flexible wall, such as in the form of a flexible wall of a flexible bladder. The flexible bladder also defines a pressurization cavity within the pressure containment structure that is separated from the passage by the sealing wall. The pressurization cavity is in fluid communication with the passage through the fluid port, so that when the pressurization cavity is pressurized with the hydrodynamic bearing fluid, the hydrodynamic bearing fluid is injected into the passage through the fluid port.
In addition to the annular sealing structure, the annular pressure containment structure is versatile in that any number of different wellhead components can be assembled into the annular pressure containment structure along with the sealing structure to provide various wellhead features for different well operations. For example, the annular pressure containment structure can include components to facilitate circulation of a working fluid and drill cuttings out of the well during drilling operations and for reducing the potential that drill cuttings will detrimentally interfere with operation of the annular sealing structure.
In another aspect, the invention involves a well assembly for drilling or other manipulation of pipe in a well under pressure. In one embodiment, the well assembly includes the annular pressure control assembly operably connected to the well, typically through a flange connection to a casing string, so that the passage through the annular pressure containment structure is aligned with an interior space in the well for communication of pipe through the passage into and out of the well. In one embodiment, the well assembly includes a pipe received in the passage through the annular pressure containment structure, so that the pipe is manipulable under pressure for movement at least translationally into and out of the well and preferably also rotationally about a longitudinal axis of the pipe.
In another aspect, the invention involves a method of manipulating a pipe in a well. In one embodiment, the method includes disposing a distal end of a pipe in a well through the annular pressure containment structure so that a proximal end of the pipe remains outside of the well. The pipe is manipulated while a hydrodynamic bearing fluid is injected adjacent the pipe to help maintain an annular seal around the pipe and to help lubricate between the pipe and the sealing wall. The manipulation of the pipe could include, for example, translating the pipe into or out of the well or rotating the pipe about a longitudinal axis of the pipe, such as would normally occur during drilling operations. In one embodiment, a working fluid is circulated through the interior conduit of the pipe into the well and out of the well through the annular space surrounding the pipe. The circulating fluid, and also drill cuttings in the case of drilling, are removed from the annular pressure containment structure through a fluid port in fluid communication with an annular space in the annular pressure containment structure that is located between the sealing wall and the well. In one embodiment, at least a portion of the hydrodynamic bearing fluid is directed into the annular space to mix with the working fluid and to be withdrawn from the annular pressure containment structure along with at least a portion of the working fluid.
After producing hydrocarbon fluids from wells drilling and/or otherwise manipulated with the present invention, the produced hydrocarbon fluids could be subjected to downstream processing to prepare an upgraded hydrocarbon product. In another aspect, the invention involves a method for preparing such an upgraded hydrocarbon fluid product. In one embodiment, the method includes drilling a well into a hydrocarbon-bearing subterranean formation and extracting a hydrocarbon fluid from the subterranean formation through the well. The drilling step includes at least drilling with a drill bit connected to a distal end of a pipe extending through the passage of the annular pressure containment structure and into the wellbore. The method according to this aspect of the invention could also include among other things the step of refining the hydrocarbon fluid to produce a refined hydrocarbon product.
In another aspect, the present invention involves an assembly and method useful for drilling an anchor hole for a well from a subterranean excavation. In one embodiment, the assembly comprises an annular pressure containment structure fastened to a surface of the subterranean excavation by rock bolts. In the situation where the well is to be drilled in an upward direction, the assembly would be fastened to a portion of the roof of the subterranean excavation, while the assembly would be fastened to a portion of the floor for a well to extend down from the subterranean excavation. The annular pressure containment structure includes an interior passage adapted for receiving a pipe that is rotatable to drill the anchor hole, a fluid port in fluid communication with the passage through which drill cuttings are removable from the passage during the drilling, and a shield located between the surface of the subterranean excavation and the fluid port for directing the drill cuttings to the fluid port. In one embodiment of the method, the assembly is used to drill the anchor hole through rotation of the pipe extending through the annular pressure containment structure with a bit attached to the distal end of the pipe to dislodge pieces of rock as drill cuttings, which drill cuttings are then removable through the fluid port. To cool the bit and to assist removal of cuttings through the fluid port, a working fluid can be circulated through the interior flow conduit of the pipe and the drill bit, into the passage in the annular pressure control assembly and ultimately out through the fluid port. The working fluid could be a liquid, such as an aqueous liquid, or could be a gas, such as air.
In another aspect the present invention involves an assembly and method for securing casing pipe, such as for example securing anchor casing to support drilling of a well at an upward angle from a subterranean excavation. In one embodiment, the assembly includes a cementing unit connected to the proximal end of the casing pipe to be cemented. In this embodiment, the cementing unit comprises an interior volume in fluid communication with an interior space of the casing pipe, a plunger movable within the interior volume of the cementing unit and into the interior space of the casing pipe, and a fluid port in fluid communication with the interior volume of the cementing unit and through which cement is introducible into the interior volume between the plunger and the interior space of the casing pipe. According to one embodiment of the method, the plunger is moved from the interior volume of the cementing unit into the interior space inside the casing pipe to force at least a portion of the cement out of the distal end of the casing pipe and around the outside of at least a portion of the casing pipe disposed in the hole.
In another aspect, the present invention involves an assembly and a method for perforating a well, such as for example a well drilled at an upward angle from a subterranean excavation. In one embodiment, the assembly includes a pipe longitudinally extending from a proximal end located outside of the well to a distal end located in the well, with the pipe having an interior conduit for directing the flow of fluid through the pipe between the distal end and the proximal end, with a seal across the interior conduit at some location between the distal end and the proximal end that prevents the flow of fluid from the distal to the proximal end of the pipe. In this embodiment, a perforating unit is connected to the proximal end of the pipe, with the perforating unit containing a propellant and at least one projectile, wherein the perforating unit is actuatable to ignite the propellant, causing the projectile to be propelled in the direction of the seal to puncture a hole through the seal to permit the flow of fluid through the interior conduit from the distal end of the pipe to the proximal end. In one embodiment of the method, the perforating unit is actuated to perforate one or more hole through the seal, thereby permitting fluids from a hydrocarbon-bearing formation to flow through the interior conduit of the pipe to be produced from the well.
In another aspect, the present invention involves an assembly and a method concerning securing pipe in a wellhead of a well that extends upward from a subterranean excavation so that the pipe in the well is in compression rather than in tension as is the case with conventional wells that extend downward from a surface location. In one embodiment, the assembly includes a wellhead assembly connected to a casing pipe extending at least some distance into a well, with the wellhead assembly including a plurality of collets that can be wedged against pipe that extends from the wellhead assembly through an interior space of the casing pipe in the well. When wedged against the pipe, the collets secure the pipe in place, with the pipe being in compression, because the distal end of the pipe in the well will be at a vertically higher location than the portion of the pipe secured by the collets. In one embodiment of the method, the distal end of the pipe to be secured is translated through a wellhead assembly and into a well to which the wellhead assembly is connected, with a proximal end of the pipe not passing through the wellhead assembly and remaining outside of the wellhead assembly with the proximal end of the pipe being located vertically lower than the distal end of the pipe. In this embodiment, the collets are then wedged around the outside of a portion of the pipe disposed in the wellhead assembly to secure the pipe.
In another aspect, the present invention involves a method for recovering hydrocarbon fluid from a subterranean hydrocarbon-bearing formation, such as in a petroleum or gas reservoir, through a well extending in an upward direction into the formation from a subterranean excavation located below the formation. In one embodiment, the method involves draining hydrocarbon fluid from the well through a production pipe extending into the well while simultaneously injecting water into the formation through the annular space in the well outside of the production pipe. In a preferred situation, the production pipe extends upward above a hydrocarbon fluid-water contact (e.g., oil-water contact or gas-water contact) in the formation, with the hydrocarbon fluids being drained from the formation above the contact and the water being injected into the formation below the contact. In one embodiment, at least a portion of the water is recycled water produced from the formation along with hydrocarbon fluid, with the produced fluid being transported to the surface for separation of the water followed be piping at least a portion of the water back into the subterranean excavation for injection into the well.
In another aspect, the present invention involves a bit retainer for use in drilling operations for drilling a well in an upward direction. In one embodiment, the bit retainer includes a space into which a bit is retractable. The shape of the retraction space is keyed to correspond with the shape of the bit, so that the bit retainer and the bit cannot rotate relative to each other when the bit is retracted into the retraction space of the bit retainer. This permits the pipe to be threaded onto and unthreaded from the pipe without removing the bit from the annular pressure containment structure of the present invention.
In another aspect, the present invention involves an assembly useful for producing hydrocarbon fluids from wells drilled in an upward direction from a subterranean excavation. The assembly permits the wells to be connected to a closed collection system in the subterranean excavation. The collected hydrocarbon fluids, and any accompanying produced water, can then be transferred to the surface for storage and/or treating.